Coaxial fluid lines have long been used in industry to deliver various fluids from a source to a point of utilization. Oil and air, for example, are quite commonly delivered in coaxial lines to power and lubricate air-driven tools, motors, and the like. Such systems generally include coaxial fluid transmission lines connected from the tool to a manifold block, an injection lubricator, or the like, when the oil and air is introduced from separate sources. The lines are generally provided with threaded connector ends which are threadably received on the tool and the manifold block. Replacement of the tool or disconnection from the manifold block requires that at least one of the threaded ends be removed by the use of a wrench or the like. In other applications, coaxial tubing utilized to deliver various fluids to a nozzle or the like where it is mixed or misted for lubrication of cutting tools or similar applications. In either event, it is very desirable to have a coupling, and particularly a "quick-disconnect" coupling, for connecting and disconnecting the coaxial supply lines as a unit such that the tool, nozzle, or other item to which the individual fluids are delivered in the coaxial tubing may be readily removed or connected; however, whereas quick-disconnect couplings have long been in use for single fluid tubes, no suitable such device has heretofore been available for coaxial pairs of tubes or lines.